Titanium alloys



United State P t F TITANIUM ALLOYS Earl F. Swazy, Richard H. Freyer, and Lee S. Busch, Indianapolis, Ind., assignors, by mesne assignments, to Mallory-Sharon Titanium Corporation, Indianapolis, Ind., a corporation of Delaware No Drawing. Application September 4, 1953, Serial No. 382,183, now Patent No. 2,786,756, dated March 26, 1957, which is a division of application Serial No. 138,516, January 13, 1950, now Patent No. 2,661,286, dated December 1, 1953. Divided and this application February 15, 1957, Serial No. 644,431

3 Claims. (Cl. 75175.5)

This invention relates generally to alloys of titanium and has particular reference to alloys consisting of titanium, carbon and silicon, alone, or in combination with another element, to form a quaternary alloy with titanium predominating. This application is a divisional application of Serial No. 382,183, filed September 4, 1953, now Patent No. 2,786,756, dated March 26, 1957, which in turn is a division of application Ser. No. 138,516, filed January 13, 1950, now Patent No. 2,661,286, dated Deeember l, 1953.

An object of the present invention, therefore, is to provide wrought, ductile alloys of titanium.

Another object of the present invention is to provide a wrought, ductile alloy of titanium, carbon and silicon.

Still another object of the invention is to provide quaternary alloys of titanium.

Yet another object of the invention is to provide alloys of titanium consisting of titanium, carbon and silicon having greater resistance to oxidation at elevated temperatures than pure titanium and exhibiting good hardness characteristics thereof.

Another object of the invention is to provide an alloy of titanium consisting of titanium, carbon and silicon and any one of the following elements: aluminum, copper, vanadium, chromium, boron, tungsten and iron.

Yet another object of the invention contemplates a method of preparing quaternary alloys of titanium consisting of the ternary alloys of carbon, silicon and titanium, to which is added an element from the group; aluminum, copper, chromium, vanadium, boron, tungsten or iron.

The invention, in another of its aspects, relates to the novel features and principles teaching the objects of the invention and to the novel principles employed herein whether or not these features and principles may be used in said object or in said field.

it is found that alloys of titanium, silicon and carbon with titanium predominating as a ternary alloy, or as an alloy to which may be added another element such as aluminum, chromium, copper, vanadium, boron, tungsten or iron provide a resistance to oxidation at elevated temperatures greater than that of pure titanium. Such alloys provide ductile, strong alloys of titanium and exhibit good corrosion resistance and high hardness characteristics at elevated temperatures. These alloys are usually manufactured by melting and casting in a graphite retort under an inert or neutral atmosphere; for example, argon, or in a vacuum. Further, the alloys may also be prepared by powder metallurgy methods. Thus, as an example, alloys containing .1% to silicon, .2% to 2% carbon with the balance titanium, as compared to pure titanium, are characterized by having a higher tensile strength, equiv alent ductility, slightly higher electrical resistivity, much better resistance to oxidation at elevated temperatures and high hardness at temperatures up to 600 C. Further they may be hot or cold worked by the usual methods known to the art.

As a further example, hereof, an alloy made by mixing silicon powder and titanium powder or sponge, and melting and casting in graphite in argon gas, contained 0.992% silicon, .47% carbon, with the balance titanium. This alloy had the following properties as hot forged to 80% reduction in area (equivalent properties of titanium containing .477% carbon only are included for comparison),

Moreover, alloys, such as above, are characterized by a unique response to heat treatment. Upon quenching from 1000 0., these alloys do not harden appreciably (most alloys of titanium which contain metals forming stable carbides do harden on quenching). However, as the tensile strength is lowered to 113,500 p. s. i., the elongation increases to 16.5%. In the as forged condition, the hardness at 600 C. increases from 0 Rockwell A to 32 Rockwell A when quenched. These changes are apparently caused by the presence of large amount of B titanium (body centered cubic) which is not transformed to a on fast cooling from 1000 C.

Again, in resistance to scaling tests at 900 C., an alloy containing .992% silicon was three times as efiective as that for titanium containing .47% carbon. The results revealed a 536% increase in weight for the silicon alloy and 1.89% for the titanium alloy containing carbon only.

Still other alloys may be fabricated of titanium, chromium, silicon, and carbon. These are also formed as by melting and casting under an inert or neutral atmosphere (for example, argon) or in a vacuum. Again, such alloys may also be prepared as by powder metallurgy methods. For example, in the fabrication of this alloy, a preferred method consists of mixing chromium and silicon, in massive or powder form, with titanium in sponge or powder form and melting and casting in graphite. The source of the carbon, once more, is the crucible and the amount thereof is easily controlled as by varying the time that the charge is molten. The alloys of titanium, carbon, chromium and silicon are preferably forged in air at temperatures between 800 C. to 900 C. but may be hot or cold worked by methods known to the art.

Such alloys contain small but significant amounts of chromium, silicon and carbon; that is, up to 10% chromium; up to 5% silicon and up to 2% carbon with the balance being titanium. The lower limit is 0.1% chromium, 0.1% silicon, 0.1% carbon and the balance titanium. A practical range of this composition is from 1% to 5% chromium; from .5 to 2% silicon; from 0.3% to 0.7% carbon and the balance titanium.

Alloys of titanium, carbon, chromium and silicon by this invention have the following minimum properties:

Ultimate tensile strength p. s. i-.. 125,000 Elongation in 2" percent 5 Modulus of elasticity p. s. i 18 10 Electrical resistivity .ohm-cm X10" The following chart is useful in depicting the constituents of the above described alloys.

'lfhus it is sgenjhagbyg the present invention primary, il r y o si ffi tanium liconl nsl arwnlmay be formed presenting characteristics substantially superior to pure titanium in matters of resistance to oxidation, resis tanqe, to, corrosion; and; high hardness. Inv addition, these ternary, alloys, may be combined with. chromium. Thus, a;bjasic; ternary alloy consists. offrom .1%-to 10%.

silicon; fro rn ,.2 to'2l%;- carbon with the remainderbeing substantially; 31h titaniumr A quaternary. alloy may; consist oftup to 10% silicon; up to 2% .carbon; and up to 10% chromium, the remainder being substantially all titanium. Whiletthe present invention as to its objects is merely illustrative andinotezrhaustive in scope and since many widely difierentlembodimcnts of the invention may be made without departing from the scope thereof, it is intended that all matter contained inthe above description bejnterpreted-asillustrativeandnot in a limiting sense.

What is claimed is:

A lq s qnt n n q n 0 to 0% chromium. from 0.1% to 5% silicon, from 0.1% to 2% carbon, and the balance thereafter being substantially all titanium.

2. Alloys containing from 1% to 5% chromium, from 5% to 2% silicon, from 0.3 %to 0.7% carbon, and the balance being substantially all titanium, said alloys being.

quench hardenable.

3; Alloys of titanium as in claim 2 havingthe following minimum properties:

Ultimatettensile strength p. s. i 125 ,00 0 E on a on n. +.----raw-"p e t" 5 Modulus of elasticity p. s. i 18. 1 0' Electrical resistivity ohm-cm.. 75 X 10- No references cited. 

1. ALLOYS CONTAINING FROM 0.1% TO 10% CHROMIUM. FROM 0.1% TO 5% SILICON, FROM 0.1% TO 2% CARBON, AND THE BALANCE THEREAFTER BEING SUBSTANTIALLY ALL TITANIUM. 